Cohesive sheet

ABSTRACT

THIS COHESIVE SHEET MATERIAL WHICH CAN BE USED AS A BANDAGE, TAPE, CLOSURE OR THE LIKE, COMPRISES A POROUS, RESILIENT, OPEN-CELL CELLULAR WEB SUCH AS POLYURETHANE FOAM HAVING A CELL DENISTY OR PORE COUNT IN THE RANGE OF ABOUT 10 TO 120 CELLS OR PORES PER RUNNING INCH, THE CELLULAR SURFACE AREA ON AT LEAST THE EXPOSED EXTERIOR THEREOF OCCUPYING LESS THAN ABOUT 15% OF THE TOTAL AREA OF SAID EXTERIOR, PREFERABLY LESS THAN 5%. THE CELL SURFACES THROUGHOUT SAID CELLULAR WEB ARE COATED WITH A NONPORE-FILLING, NON-TACKY COHESIVE COATING. COMPRESION OF THE WRAPPING SUBSTANTIALLY INCREASES THE COATED CELLULAR SURFACE AREA ON THE EXPOSED EXTERIOR OF THE WRAPPING AND THEREBY INCREASES THE COHESIVENESS OF SAID WRAPPING RELATIVE TO A CONTACTING COHESIVE SURFACE.

March 14, 1972 J, uEsE COHESIVE SHEET Filed May 22, 1970 F/Gl.

FIG. 2.

FIG .4.

FIG. 3.

22 D INVENTOR GEORGE J. BUESE BY? A/aMMZJhw/rwu ATTY United States Patent 3,649,436 Patented Mar. 14, 1972 U.S. Cl. 161160 Claims ABSTRACT OF THE DISCLOSURE This cohesive sheet material which can be used as a bandage, tape, closure or the like, comprises a porous, resilient, open-cell cellular web such as polyurethane foam having a cell density or pore count in the range of about 10 to 120 cells or pores per running inch, the cellular surface area on at least the exposed exterior thereof occupying less than about of the total area of said exterior, preferably less than 5%. The cell surfaces throughout said cellular web are coated with a nonpore-filling, non-tacky cohesive coating. Compression of the wrapping substantially increases the coated cellular surface area on the exposed exterior of the wrapping and thereby increases the cohesiveness of said wrapping relative to a contacting cohesive surface.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a wrapping or sheet material which will cohere to itself simply by the application of moderate pressure. More specifically, in certain advantageous embodiments, it relates to a medicalsurgical wrapping in the nature of a cohesive bandage, tape, closure or the like, which is highly conformable, very porous, readily cut or contoured, neat in appearance, lightweight and non-bulky, protective, capable of being repeatedly removed and replaced, and inexpensive to produce.

While the present invention will be described in connection with particular embodiments designed for application in the medical-surgical field, it should be understood that the invention is not limited to such particular embodiments. It can be employed for various other home, commercial and industrial applications, as will become apparent to those skilled in the art as the description thereof proceeds.

Description of the prior art Techniques for holding surgical pads, bandages and the like, in place vary depending upon the specific application involved. Surgical dressings, for example, may be held in place by an overwrap bandage which in turn is tied, taped or clipped in place. Such techniques, however, often leave much to be desired. For example, the overwrap bandage sometimes creates conformability problems and undesired immobilization of the member being wrapped. After wrapping, the bandage must still be held in place by tapes, clips, or ties, which of themselves present problems. Thus, for example, the tacky adhesive surface of conventional tape presents handling and unwind problems and collects lint, dirt and dust, thereby decreasing adhesion and presenting antiseptic problems. Because of the quick gra characteristic of the exposed tacky surface, it is difiicult to adjust and reposition the tape as it is applied. Adhesion of the tape to the underlying skin often leads to painful problems of removal.

To cope with such well-known problems, cohesive bandages have been developed, but they also suffer from one or more shortcomings. For example, they are less conformable and less porous than required and do not appear as neat as desired. Some involve complex structures which are relatively costly to produce and have not been widely accepted.

It is therefore a general object of the present invention to provide an alternative to conventional bandages, tapes, ties, closures and the like, which does not suffer from such shortcomings of prior art structures. It is another general object to provide a new concept in such products which permits the structure to be tailored to the requirements of the particular end use.

A more specific object of the present invention is to provide a low cost, highly-conformable cohesive wrapping which is non-sticky and non-tacky to the touch and yet will stick to a similar cohesive wrapping upon the application of light or moderate pressure. It is another specific object to provide a highly versatile, non-fouling, non-laminated, flexible wrapping which has good unwind properties and no requirement for an interliner. It is another specific object to provide a double-faced pressuresensitive tape which is substantially free of quick grab and can be readily cut and contoured to meet specific requirements.

It is another specific object to provide a highly porous, stretchable cohesive bandage which may be readily removed and reused without substantial loss of cohesiveness. It is a still further object of the present invention to provide a low cost, non-laminated cohesive bandage which adds a protective layer to the area bandaged. These and other objects of the present invention will become apparent as a detailed description thereof proceeds.

SUMMARY OF THE INVENTION These objects are achieved in a particular embodiment by a cohesive wrapping which comprises a porous, resilient, open-cell cellular web having a cell density or pore count in the range of about 10 to cells or pores per running inch (abbreviated p.p.i.), the cellular surface area on at least the exposed exterior thereof occupying less than about 15% of the total of the exposed area, preferably less than 5%. The cell surfaces throughout the cellular web are coated with a substantially nontacky cohesive coating which is substantially non-porefilling so that the open cell nature of the web is maintained. Compression of the coated cellular web thus substantially increases the surface area of the mass on the exposed exterior thereof and thereby substantially increases t-he cohesiveness of the wrapping relative to a contacting cohesive surface.

The cellular web The cellular web of the present invention can be any conventional highly-porous, resilient, stretchable, conformable cellular web having the requisite characteristics, the particular web per se not being part Oif the present invention other than being a necessary part of the claimed construction. Flexible polyurethane foams are preferred, although certain functionally equivalent foams such as, for example, certain vinyl foams, styrene-butadiene foams and possibly some rubber-based foams may be substituted. Foams which are closed cell but otherwise having the requisite characteristics may be treated, by methods known in the art, to open up sufficient of the cell structure to permit their use. This may be done chemically or mechanically as by bursting or perforating.

The percent of open cells in the foam should be high enough to provide proper mass impregnation substantially throughout the foam. It must also be of the proper degree to permit the uncoated foam to rapidly regain its original shape after compression. Though it is not necessary for some applications, it is desirable for cohesive bandage applications against the body, to have the degree of openness of the cell structure adeequate to permit cohesive bandages made from this foam to breathe Well even after being overlapped and compressed. At the present time there does not appear to be an adequate test to determine just what the minimum degree of open cell structure the foams should have; however, the above requirements suggest a substantial percentage of the cells should be open, it generally being preferred to use foams having at least 50 percent or more open cells. The preferred products use foams having a completely open cellular strucure.

The preferred flexible, resilient, conformable open-cell polyurethane foams may be either polyester or polyether polyurethane, typically having a density in the range of of about 0.5 to 6 pounds per cubic foot and a pore count in the range of about 10 to 120 p.p.i., preferably about 20 to 100 p.p.i., and optimally in the case of medical-surgical embodiments about 60 to 85 p.p.i. Polyester polyurethane foams are preferred because cell size maybe more readily controlled and because of superior tensile strength. A suitable polyester polyurethane foam may be prepared, for example, as set forth in Example II of US. Pat. 2,956,310.

A fundamental requirement of the present invention is that the Web have less than about cellular surface area, and preferably less than about 5% cellular surface area, on exposed sunfaces, the balance being open voids. In practice, a uniform web is preferred wherein the cellular surface area in any given plane in the web is less than about 10% of the total area in that plane, and preferably less than about 5%, e.g., about l3%. As a result, with so very little cellular surface area in any given plane and with a relatively thin cohesive coating thereon, only a very small fraction of the total area is available for mass-to-mass contact. Accordingly, if the coated Web of the present invention is in roll form, having been wound without excessive tension, there would be very little mass on the surface of one layer of the roll in contact with the mass of the contacting layer. The resulting roll thus has excellent unwind characteristics.

Compression of the web, however, brings a great increase in the coated cellular surface area, and thus mass, on the exposed surface in contact with a compressed, opposed cohesive surface, thereby resulting in good cohesion. Also, some intermingling or entangling of the strands or ribs of the cellular materials would take place, thus adding to the apparent cohesiveness.

To achieve the low surface area in any given plane, pore counts in the range of about 10 to 120 p.p.i., preferably to 100 p.p.i., have been found operable. Foams with the larger pores, e.g., 10 to 30 p.p.i., are somewhat harsh to the feel but for many purposes such characteristic is not disadvantageous. For example, such large-pore webs can be used for binding purposes similar to the use of the Well-known Ace bandage. The large-pore material also finds use in the closure field. Manifestly, the large size pores also permit thicker mass coatings with out adversely decreasing porosity or encountering undesired filling of pores.

The lower limit on pore size (high pore counts) is dictated in part by unwind problems associated with fine pores. As the pore count goes up, the cellular surface area in any plane tends to increase; and when this cellular surface area is coated with cohesive mass, the area of mass available for contact in any given plane is increased to a still greater extent. As a consequence, foams having pore counts above about 120 p.p.i. are generally unsatisfactory for present purposes. In addition, at the higher mass densities (thicker mass coatings) undesired decrease in porosity or filling of the pores may be encountered.

The reticulated foams which are substantially free of cell walls are preferred because of the reduced surface area in any given plane and the greater ease with which 4 such foams can be coated with the cohesive mass. Nonreticulated and substantially non-reticulated foams have, however, been employed successfully and are preferred from a cost standpoint.

The thickness of the web depends upon its end use. Cohesive bandage material may run in the range, for example, from about 3 inch to A; inch, preferably about inch to 4 inch. For cushioning purposes, substantially thicker foams may be employed, e.g., about Vs inch to /3 inch.

Open cell polyurethane foams useful in preparing the structure of the present invention may be obtained from commercial sources. Examples include the various reticulated foams sold by the Foam Division, Scott Paper Company, Chester, Pa., and the substantially non-reticulated foams, e.g., 65 p.p.i. P 4104, sold by the General Foam Division, Tenneco Chemicals, Inc., New York, NY.

The cohesive coating The mass employed for coating the cellular surfaces should be cohesive in nature so that the resulting wrapping will adhere to itself, but should preferably not be of the pressure-'sensitive-adhesive type having substantial tack, that is, it should be non-adhesive in nature. Thus, the exposed surface would be non-fouling and would not pick up any dirt, dust or the like. In addition, it can be more readily positioned on the surface being wrapped. Any conventional cohesive mass may be employed so long as it has the requisite properties. In the medicalsurgical field, the mass must also have acceptable clinical properties, e.g., inert, non-irritating, non-allergy forming, and should in some instances lend itself to sterilization.

Suitable commercially-available cohesives, which are substantially non-adhesive, include the natural rubber masses such as those designated Uniroyal NC400M30" and Uniroyal l1-35X Creamed 356 as sold by United States Rubber Company, and synthetic cohesives such as Natsyn 400, 410 and 450, which are synthetic cis-polyisoprene cohesives sold by The Goodyear Tire and Rubber Company. The Natsyn cohesives are preferred because in the event of inadvertent compression of the product of the present invention, those made with the Natsyn cohesives will pop out or snap back simply by subjecting them to mild heating, e.g., F., for about 5 to 15 minutes. In contrast, products made with the rubber cohesives will often remain compressed even after heating to as high as 350 F. Both the Natsyn and rubber cohesives are, however, steam 'sterilizable, thus enhancing their use in the medical-surgical embodiments.

The formulation of the cohesive masses can be adjusted to decrease or eliminate any residual tackiness, by, for example, the addition of silicone fluids, e.g., l to 10% of Dow Corning 200 Fluid (a dimethyl siloxane polymer sold by Dow Corning Chemical Products Division, Dow Corning Corporation, Midland, Mich.) at 12,500 centistokes (25 C.), or G. E. Viscasil 100,000 Silicone Fluid (a dimethyl silicone fluid sold by the General Electric Company, Silicone Products Department, Waterford, New York). An antioxidant may also be added to the mass to improve shelf life, e.g., .5 to 2% of Plastanox 2246 (2,2'-methylene-bis(4-methyl-6-tertiarybutyl phenol) sold by American Cyanamid Company, Organic Chemicals Division, Bound Brook, NJ.) or "Ionol Antioxidant (2,6-di-t-butyl-4-methyl phenol sold by Shell Chemical Company, Cleveland, Ohio), preferably Plastanox 2246.

The amount of mass is dependent upon the nature of the foam, the size of the pores, the end use of the prodnot, the nature of the mass and the like. The larger the pore size in the case of reticulated foams, the lower the mass weight will be because there are fewer strands of foam to coat. For these more open foams, however, the mass coating itself might be thicker, thus offsetting at least in part the smaller surface area to be covered. In

the case of non-reticulated foams, a higher mass weight is usually required because of the greater surface area to be coated.

As a typical example, A -inch thick, 80 p.p.i. Scott reticulated foam which is coated with Natsyn 400 synthetic cis-polyisoprene having a Williams plasticity at 100 F. of 4.51 mm. and used for a general cohesive bandage may be coated to about .25 to 2.5 ounces per yard square, preferably about 0.5 to 2.0 ounces per yard square, optimally about 0.8 to 1.1 ounces per yard square. Where the bandage is not to be rolled or, if rolled, an interlining is used, relatively high mass weights may be employed. For example, the 80 p.p.i., Scott reticulated foam was coated at the level of 2.01 ounces per yard square and produced a very good cohesive bandage. In the case of the non-reticulated P4104 type foam, similar or slightly higher mass weights may be employed. For example, a good bandage was produced from such inch foam webs using about 0.8 to 0.9 ounces per yard square of Natsyn 400 having a Williams plasticity of 4.5 mm. at 100 F.

For the large-pore foams, e.g., 1030 p.p.i., much greater mass weights may be employed without unduly decreasing porosity or plugging pores. For example, successful cohesive wrappings have been prepared from As-inch thick, 20 p.p.i., Scott reticulated foam with mass weights in the range of about 1 to 10 ounces per square yard.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the following detailed description of specific embodiments, read in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates in magnified cross section a fragmentary portion of the cohesive wrapping of the present invention in the uncompressed condition;

FIG. 1A is a greatly-magnified cross section of a single coated cell strand of the cohesive wrapping;

FIG. 2 is a plan view of a disc-shaped portion of the embodiment of FIG. 1 showing only the coated cell surfaces which are at the upper exterior surface thereof;

FIG. 3 is similar to, and on the same scale as, FIG. 1 and illustrates the wrapping in compressed condition;

FIG. 4 is a plan view of a disc-shaped portion of the embodiment of FIG. 3, again showing only the coated cell surfaces which are at the upper exterior surface when the structure is compressed; and

FIG. 5 is a schematic diagram illustrating one method of producing the embodiment of FIG. 1 of the present invention.

It should be understood that the subject matter is illustrated and represented in the drawings by graphic symbols and that the drawings are not to scale. As a result, the representations necessarily depart from the actual appearances of the various structures.

DETAILED DESCRIPTION OF THE DRAWINGS INCLUDING PREFERRED EMBODIMENT Referring to FIGS. 1 and 1A, the cohesive wrapping comprises highly-porous, reticulated polyurethane foam 10, which is made up of cellular strands 12 coated with a layer of cohesive mass 14. The upper surface 16 and the lower surface 18 are shown in cross section as solid lines but actually represent a highly porous surface, only a very small percentage of which, i.e., less than Williams plasticities are determined with a Williams Plastometer at 100 F. (or other selected temperature) using a ball of mass weighing 2 grams placed between two opposed plates protected with controlled thickness paper. A 5 kilogram weight is applied. Separation of the plates is measured after about minutes. adjustment being made for the thickness of the paper. The greater the se aration the greater the plastieity of the material. The ball of mass is preconditioned in the plastorneter oven for 14 to 15 minutes prior to running the plasticity test.

preferably lass than 5%, constitutes coated cell strands and cell walls, the remainder being open void spaces.

This is graphically illustrated in FIG. 2 which shows only those coated cellular strands in the plane of the upper surface of the cohesive wrapping of 'FIG. 1. It is readily apparent that the total area of mass in the plane of the upper surface represents only a small fraction of the total area, e.g., about 1 to 3%. Accordingly, the web can be wound on itself under slight tension and readily unwound because of the extremely small mass-to-mass contact.

FIG. 3 shows wrapping 10 in a compressed condition wherein the cell walls or strands are forced together, presenting at surfaces 16 and 18 many additional cell strands which previously had been disposed in the interior. As a result, the total mass area at the surface is increased manyfold that encountered in the uncompressed condition, as illustrated in FIG. 4. This increased mass 'area is sufiicient to give good cohesion.

FIG. 5 illustrates another advantage of the present invention, that is, the simplicity of producing the same on a continuous production scale. A web 20 of porous reticulated foam is unwound from supply roll 22 under only slight tension. After passing over direction changing rollers 24 and 26, it is introduced in the gap between engraved steel coater roll 28 and rubber roll 30. The lower portion of roll 28 is immersed in mass solution 32 in vessel 34. The mass is thus transferred from the surface of roll 28 to and through foam 20 forming a bank of mass 35 at the nip of rolls 28 and 30. The gap between rolls 28 and 30 is adjusted so that the foam is compressed and a metered quantity of the mass is forced throughout the foam so as to coat substantially all of the cell surfaces. If the foam were not so compressed, there would be a good possibility of many of the pores remaining filled with mass.

The mass-coated foam then passes into drying oven 36 where it is dried and then accumulated on product roll 38. Oven 36 may operate, for example, at a temperature of, for example, 250 F., and the residence time of the mass containing foam therein may range, for example, from about 1 /2 to 2 /2 minutes. The product is accumulated on roll 38 with substantially no tension so as to avoid substantial compression thereof. It thus may be readily unwound therefrom with little required tension. Thus, for example, the unwind tension of the finished product may range from 0.2 ounce per inch width to 2.0 ounces per inch width. When identical samples of the product are overlapped and compressed, however, the peel cohesion rises to as much as 4 to 20 ounces per inch width.

The present invention will be more clearly understood from the following specific examples.

EXAMPLE 1 Three samples of the product of the present invention were produced using ;-inch thick, p.p.i., Scott reticulated foam and Natsyn 400 cis-polyisoprene mass having a Williams plasticity at F. of about 4.53 mm., said mass containing about 1% Plastanox 2246 antioxidant. The mass was applied in the form of a xylene solution at several different solids contents, as indicated hereinafter. The mass was spread on silicone-coated paper, i.e., 3-mil Daubert KG-6, using a bar coater at a very open setting, i.e., about 24 mils. The foam was then applied to the wet mass surface and another sheet of same silicone paper placed on top. The composite was rolled very hard to force the mass through the foam until the surface of the upper silicone-coated paper was completely wetted. Both silicone-coated papers were then discarded and the masscontaining foam dried in a steam cabinet at about 160 F. for 15 minutes. The mass weight in the dried product was recorded as hereinafter set forth.

A l-inch strip of each sample was placed on top of an identical strip and a 10-pound roller passed once thereover at 12 inches per minute. The composite was then peeled apart at an angle of and at 12 inches per minute in order to measure the peel cohesion. The results were as follows:

Peel

Percent Mass cohesion, solids in weight, oz./in. xylene oz./yd 2 width The peel cohesion in each case is considered highly satisfactory. Each sample was found to be highly comformable and porous, had no undesired tack and was very easy to unwind from 2. rolled form. It could be readily cut or slit to desired dimensions and could be repeatedly overlapped and squeezed together and pulled apart and still show satisfactory cohesion.

EXAMPLE 2 Three samples of the product of the present invention were produced on apparatus similar to that already described in connection with FIG. 5. The foam used was 62-mil, 8O p.p.i., Scott reticulated foam. A low solids solution of Natsyn 400 synthetic cis-polyisoprene in xylene, said solution containing about 1% Plastanox 2246 antioxidant, based on the weight of the rubber, was rolled into the foam. The impregnated foam was dried by passing the same at the rate of about 14 feet per minute through a 25-foot oven at 250 F.

Peel cohesion was determined as described in Example 1. In addition, unwind tension was determined after aging at room temperature for at least 1 /2 months. The results were as follows:

Peel Unwind Coater Mass cohesion, tension, oz.,in. oz./in.

width width EXAMPLE 3 Three samples of the product of the present invention were prepared using A; -inch thick sheets of about 20 p.p.i., Scott reticulated foam weighing about 2.6 to 2.67 ounces per yard square. The cohesive mass used was Uniroyal NC40OM3O rubber latex in aqueous dispersion. The solids content was either 31% or 62%, as hereinafter indicated. The foam was immersed in the latex and then passed between opposed rolls set at varying gaps, as hereinafter indicated. The resulting mass-containing foams were dried in a steam cabinet at about 160 F. for about 15 minutes.

Peel cohesion was determined substantially as in Example 1. The results were as follows:

Peel

Approx. Mass cohesion Percent solids in aqueous roller weight, Or /1n: dispersion gap, mils oz.1yd.= width The peel cohesion in each case is considered highly satisfactory. Each sample was found to be very porous and highly conformable, had no undesired tack and was extremely easy to unwind.

8 MISCELLANEOUS APPLICATIONS In addition to its use as a bandage or a tape in the medical-surgical field, the product of the present invention lends itself to a number of other product uses. For example, it would make an excellent closure for disposable items such as disposable surgical gowns, disposable diapers and the like. It may be used to hold various items in place on the body. For example, it has been used successfully holding eye shields in place. As suggested earlier, it may also be used as a replacement for the conventional fabric elastic bandage. For additional strength stronger foams can be laminated to the soft foams in order to combine strength and good feel.

In its thinner form, the tape can be used as an underwrap for strapping tapes, In fact for such purposes the mass may advantageously have adhesive properties as well as cohesive properties. The resulting moderate adhesion would tend to hold the underwrap in place on the skin. Where adhesive properties are desired the foam may be impregnated with a pressure sensitive adhesive together with, or in place of the cohesive material. The manner of impregnation and the degree of foam strand coating would otherwise be the same.

The product may also be used as an industrial strapping tape for various uses including general packaging and even Christmas packaging. For such purposes the tapes can be reinforced to meet specific requirements by, for example, laminating thereto strengthening fabrics, coatings, fibers and the like. Other modifications may be incorporated to achieve desired characteristics.

From the above description, it is apparent that the objects of the present invention have been achieved. While only certain embodiments have been illustrated, many alternative modifications and equivalents will be apparent from the above description to those skilled in the art. These other alternatives and equivalents are considered Within the spirit and scope of the present invention and coverage thereof is intended by the claims of any patents based on this application and any continuations or divisions thereof, even though not necessarily encompassed by the verbiage thereof.

I-Iaving described the invention, what is claimed is:

1. A unitary, substantially uniform cohesive sheet comprising:

(a) a porous, resilient, open-cell cellular web having a cell density in the range of about 10 to 120 cells per running inch, the cellular surface area on at least the exposed exterior thereof occupying less than about 15% of the total area of said exterior when said web is non-compressed; and

(b) a non-pore-filling cohesive coating on the cell surfaces substantially throughout said cellular web; whereby compression of said sheet substantially increases the coated cellular surface area at the exposed exterior and thereby substantially increases the adhesion characteristics of said sheet.

2. The cohesive sheet of claim 1 wherein the coated cellular web has less than about 15% coated cellular surface area in any given plane when non-compressed.

3. The cohesive sheet of claim 1 wherein said web comprises open-cell polyurethane foam.

4. The cohesive sheet of claim 1 wherein said cellular web is substantially uniform in cross section.

5. The cohesive sheet of claim 1 wherein said cohesive coating has adhesive properties.

6. The cohesive sheet of claim 1 wherein said cohesive coating is substantially non-tacky and non-adhesive.

7. The cohesive sheet of claim 1 wherein said cohesive coating is a rubber base and contains an antioxidant.

8. The cohesive sheet of claim 1 wherein said foam comprises open-cell polyurethane foam having a pore count of about 20 to p.p.i. and a cellular surface area in any given plane when non-compressed of less than about 5%.

9. The cohesive sheet of claim 1 wherein said cohesive coating comprises synthetic cis-po1yisoprene.

10. The cohesive sheet of claim 1 laminated on at least one surface thereof to another flexible web.

References Cited UNITED STATES PATENTS 8/1966 Windecker l61160 2/1964 Copeland 128--156 5 WILLIAM J. VAN BALEN, Primary Examiner U.S. C1.X.R. 

